We listen to you:

• For some membrane producers, the level of Cyclic Dimer (CD) can be important to their processing efficiencies and fiber quality.
• Two new SOLVAY UDEL^® Grades address these issues.

What does too high of a CD level potentially mean to your production?:

Filtered dope solutions of UDEL^® Polysulfone become cloudy:

White solid material can clog the process filters

Cloudiness and precipitation was determined to be crystalline Polysulfone Cyclic Dimer (CD):

Cyclic Dimer in UDEL^®

Standard UDEL^® Polysulfone:

• Contains 1.50 % in weight of CD
• In solution, and in the presence of non-solvents such as pore-formers, crystallization occurs
• Even on prolonged aging, only a small amount of CD precipitates: majority (greater than 1.4%) stays in solution

New UDEL^®LCD Grade

SOLVAY has developed two LCD Polysulfone resins:

• UDEL^® P-1700 LCD
• UDEL^® P-3500 LCD (material of choice)

These new UDEL^® LCD Grades Remain clear (reduced precipitation) for a longer period of time than standard UDEL polysulfone.
For example, at 40°c, UDEL^®P-3500 LCD dope solution is 10 times clearer than UDEL^®P-3500 NT 11.

• LCD grades typically contain 1.20% CD.
• LCD grade contains all the molecules as normal PSF, and contains lower levels of oligomeric molecules.
• LCD are still In compliance with Title 21 Code of Federal Regulations CFR 177.1655

What are the benefits for our Customers to use Udel^®LCD?:

1. Economically

Less precipitation in process equipment (vessels, pumps...) resulting in :

• Longer shelf-life for dope solutions
• Longer filter life
• Less shut-downs for cleaning
• Longer continuous runs

2.Technically

• LCD resins have 10% higher Mn (Weight Average Molecular Weight) for a given Mw (Molecular Weight) offering higher fiber strength, potentially resulting in fewer fiber breakages
• Lower surface defects, and hence lower Rejects
• Higher Performing membranes

Abstract
Solutions of Polysulfone in certain solvents can become cloudy due to a slight and partial precipitation of a cyclic oligomer, which has been characterized to be crystalline cyclic dimer of Polysulfone containing two repeat units of Polysulfone. This precipitation has been a source of manufacturing problems in a number of solution processing industries such as membranes, films and coatings. MALDI-TOF Mass Spectroscopy was successfully employed to establish the presence of not only cyclic dimer but also other cyclic oligomers such as trimer, tetramer, pentamer, hexamer and so on in commercially available polyarylsulfones. Solvay Advanced Polymers has developed a proprietary process for making Polysulfone with lower levels of cyclic dimer and other cyclic oligomers. This commercially available low cyclic dimer Polysulfone resin offers a number of advantages to the solution processing industries such as long self-life, and less insoluble material that needs to be filtered. Reduction in cyclic oligomeric content also fortuitously reduced the polydispersity of the resin. For a given weight average molecular weight, increased number average molecular weights have been obtained for the low cyclic dimer resin which is expected to increase the mechanical properties of the membranes.

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